Matthew:
I'm slightly surprised by your comments. Maybe you are talking of a different kind of SAR?
The company's that do offshore and SAR are typically providing SAR for their own aircraft, hence flying in the same weather. Granted, if they are providing SAR for others then there could be a difference in the weather they fly in. What are the limits for offshore pilots compared to SAR? I think you'll be surprised how similiar they are.
As an example in the UK weather limits are as follows:
Offshore Line Pilot - JAR Ops 3 Limits
Coastguard SAR Pilot - No Limit (As long as the crew deems it safe to proceed)
Not very similar at all. A big difference in responsibility which certainly requires a higher level of experience to carry safely. At the end of the day if something goes wrong it's still your fault ...